DEVELOPMENT OF ULTRA-HIGH TEMPERATURE TESTING EQUIPMENT AND SOME MECHANICAL AND THERMAL-PROPERTIES OF ADVANCED CARBON CARBON COMPOSITES/

Advanced carbon fiber reinforced carbon (C/C) composites are one of ca ndidate materials for leading success of a space plane program in the 21st century. Though ultra-high temperature experimental studies for C /C composites have been performed, the effect of neither temperature n or heating/cooling speed on material properties have been fully made c lear yet. In this paper, high-frequency induction heating material tes ting system developed by us is presented first; the main advantage of this system is the capability of quite fast heating and cooling speed. After verifying the temperature distribution of the specimen, some ex perimental studies are performed for two types of non-oxidation-protec ted C/C composites whose heat treatment temperatures are 1600 and 3000 degrees C. Obtained results are summarized as follows; (1) Only tensi le strength tends to decrease when cooling speed becomes fast although heating speed does not have an influence upon both thermal and mechan ical properties of C/C composites. This phenomenon may be the effect o f microcracks in the matrix of C/C composites. Therefore, it is import ant to investigate the effect of cooling speed and the number of heat cycles on material properties for the practical use of C/C composites. (2) Serial data are obtained about the dependence of temperature on t ensile modulus, tensile strength and coefficient of thermal expansion. Especially, a characteristic feature of C/C composites which is so ca lled 'inverse temperature dependence of the strength' is made clear, i .e., the strength increases gradually with elevating temperature. Furt hermore, the mechanism of this phenomenon is discussed from the viewpo int of the release of residual stress.